U.S. Pat. No. 6,852,191 discloses a method and apparatus for making an adhesive-backed label whereby glassine paper stock is unwound from a roll, coated with photo-cationic silicone and cured using ultraviolet light to form a silicone coated release paper. The means of applying silicone comprises a closed chambered doctor blade. Adhesive is applied over the cured silicone layer of the coated glassine paper, cooled using a first cooling roller, then fed with a face stock to a laminator and cooled with a second cooling roller.
U.S. Pat. No. 7,608,161 discloses a method and apparatus for making adhesive-backed labels whereby glassine paper stock is unwound from a roll and coated with photo-cationic silicone and exposed to a wavelength-controlled illumination to cure. Hot melt adhesive is applied over the silicone. Simultaneously, label stock is fed with the coated glassine paper to laminating rollers where the two are joined, and the label stock is cooled using a first cooling roller and then a second cooling roller downstream. Illumination to cure the silicone is provided by a dichroic reflector.
US 2005/0089662 discloses a method and apparatus for making adhesive-backed labels whereby glassine coated paper is coated with silicone, the silicone is cured, and a hot melt adhesive is applied over the silicone layer. The glassine coated paper is then laminated to a label face stock.
U.S. Pat. No. 7,556,708 discloses a method and apparatus that forms a cut label on a liner by feeding a web of lined label material to a cutting station (either a laser cutter or anvil roller and hammer die head cutter) to cut the label material, forming a matrix around the cut label and stabilizing the label edge without vacuum, stripping the cut label from the label material and applying labels to a substrate.
U.S. Pat. No. 7,815,761 discloses a method for forming a cut label on a liner by feeding a web of unlined label material having an adhesive face to a cutting station comprised of a chilled rotating die head with multiple raised cutting edges, cutting the label material to provide a matrix around the label and stabilizing the label material with respect to the matrix without vacuum and feeding a web of liner to a set of rollers against the adhesive face of the label material.
US 2011/0036504 discloses a chilled rotating die head for cutting or perforating pressure-sensitive labels.
U.S. Pat. No. 8,163,365 (the “'365 patent”) teaches a method of forming a sheet of label material for placement on a paper object, such as a newspaper, and then subsequent removal of the label from the paper object without damaging the object. The method includes coating a water-based, pressure-sensitive adhesive on the face of a paper substrate using a gravure coater to form a repetitive dot pattern of adhesive areas. The repetitive dots assure a uniform, discontinuous coating of adhesive that allows repositioning of the label and prevents tearing of or damage to the paper surface when the label is removed, and that maintains sufficient adhesion to adhere to difficult substrates such as textured surfaces. A further embodiment of the '365 patent includes adhesive coating a release liner with the repetitive dotted pattern, providing removability of the paper label from the liner. The labels are surface printed with ink on the surface of the label opposite to which the adhesive is applied. The printed surface is further coated with a protective laminate release coating and then label shapes are die cut. The present invention improves upon the '365 patent by enabling a removable, repositionable pressure-sensitive label that can be adhered to several surfaces, including glass and plastic containers.
U.S. Pat. No. 8,076,004 (the “'004 patent”) teaches a flexible substrate, such as a paper or nonwoven substrate used for gift wrap or envelope, that is coated with a release material to enable the temporary repositioning of an adhesive applied over or on the release material. Over time, the adhesion between the release material and the applied adhesive builds so that the adhesive cannot be removed from the release material without damaging the underlying sheet material. The release material is dispersed on the flexible substrate and allows for repositioning when contacted with a pressure sensitive adhesive for at least 1 minute and not more than 10 minutes. In applications such as gift wrapping or sealing envelopes, an indefinite ability to remove the adhesive from the sheet material is not desired. Accordingly, the '004 patent permits the adhesive to bond after a short period to prevent exposing the contents of the wrapped package or envelope. The release material is selected from the group consisting of polysiloxane-acrylic block or graft polymers or polysiloxane-urea copolymers.
It is generally known in the art that printed labels with a pressure-sensitive adhesive backing are applied to plastic or glass containers for food products, health and beauty products, liquids, soaps, vitamins and other similar end-use products, among many others. The labels are made so as to require the removal of a liner, generally known as a “release liner.” A “release liner” may be made from coated or uncoated papers or polymeric films, and is typically coated with a silicone layer that enables the liner to release from the label before it is applied to a container. Removal of the release liner exposes the pressure-sensitive adhesive, permitting the label to adhere and be applied to the container with the application of slight pressure to create a strong adhesive bond between the label and container. Once applied, the conventional pressure sensitive label is not meant to be easily removed but is strongly adhered to the container surface.
The term “pressure-sensitive adhesive,” as used herein, refers to an adhesive which adheres to a surface as a result of slight application of pressure, through any known means, as opposed to thermal activation, evaporation, or absorption of a solvent to form a solid bond.
Pressure-sensitive labels can be provided in many different formats, with the most significant being a format of label face stock made from a natural or synthetic fiber paper, polymeric film, metal foil or combinations of these materials, a pressure-sensitive adhesive, and a release liner in contact with the adhesive. These three components—label face stock, pressure-sensitive adhesive and release liner—are referred to herein as “label stock material.” Labels are made using label stock material and cutting the label face stock by cutting or micro-perforating the shape of the label, by known means, e.g., a laser cutter, an anvil roller and die head cutter or other cutting method, into the label stock material, leaving a remainder portion of the label material around the cut label shape known as the matrix. The matrix is removed, leaving the labels attached to the release liner and rolled in multiple label widths into a web, then moved to a separate operation and slit into single label width webs.
The most typical format of a pressure-sensitive label comprises a laminated combination of a printed face stock that is printed on the top surface (opposite the surface to which adhesive is applied) and covered with an over-print varnish or with a laminated film layer to prevent ink rub-off; a pressure-sensitive adhesive on the back or reverse side of the face stock; and a silicone layer and backing paper liner to which the silicone layer is relatively strongly adhered. The face stock can be transparent or opaque. Opaque face stock (typically a paper face stock) can be pre-printed on the top and back sides, for instance, when a label is applied to a transparent container such as a plastic or glass bottle and is filled with a relatively transparent liquid, such as detergent or soap. The printing on the back- or reverse-side of the label face stock can then be read through the container and the product contained therein. Transparent film face stock usually is printed only on the front- or surface-side of the label, with the ink covered by a layer of protective varnish or an additional layer of transparent film. The present invention, which allows reverse-printing of the label face stock, obviates the need for overlamination of the front label surface using a varnish or additional layer of transparent film.
The conventional adhesive used in a pressure-sensitive label is water-based, requiring a relatively long air drying time. The release liner most typically used is a glassine paper coated with silicone to produce a suitable release effect between the label face stock and the release liner when the label is applied to a container or other surface. The prior art method of manufacturing such pressure-sensitive labels with silicone-coated release liner involves numerous steps and has many drawbacks. First, the roll of glassine paper has to be hung and unwound to apply silicone. The curing process involves relatively large equipment with controlled humidity and temperatures. Second, the cured release paper is then rewound and hung on a second lamination machine where adhesive is applied to the paper, laminated at another station to a printable face stock and hung in a lengthy 200-foot air drying structure to adequately cure. Following this manufacturing process, a printer unwinds the roll of label stock material to print the label face stock.
This label manufacturing process is cumbersome, involves multiple steps, large equipment, and numerous lamination steps followed by a final printing step. Moreover, this prior art makes it impossible to print on the back or reverse side of the label face stock to which the adhesive is strongly bonded. In the event of a label stock material that is desired to be printed on the back side of the label face stock, the prior art makes it necessary to strip the label face stock from the liner, print on the backside of the label face stock, and then re-laminate the face stock to the liner. The prior art in such reverse-side label printing is cumbersome and involves multiple re-lamination, printing, and de-lamination steps. Further, the prior art results in a label that makes rework or short-term removability following label application difficult to nearly impossible because of the adherence of ink to the adhesive and the container surface to which the label was initially applied. Moreover, when reverse-side printing is desired, the label face stock must be de-laminated from the release liner and printing is typically done over the adhesive. The result is blurry printing and limited graphics in order to avoid deadening of the adhesive.
U.S. Pat. No. 6,852,191 (the '191 patent) and U.S. Pat. No. 7,608,161 (the '161 patent) (collectively the “Bayzelon Patents”) attempt to improve upon the prior art manufacturing process by eliminating the need for multiple lamination passes, long silicone and adhesive curing times, and the associated unwinding and rewinding processes. The Bayzelon Patents disclose a method of manufacturing pressure-sensitive adhesive label stocks with back-side printing whereby glassine paper release stock is unwound from a roll, coated with a fast-curing, photo-cationic silicone, and exposed to wavelength-controlled ultra-violet illumination to cure. Illumination is provided by a dichroic reflector. A hot melt adhesive is applied over the silicone layer on the release paper and cooled using a cooling roller. Simultaneously, label stock is fed with the coated glassine paper to laminating rollers where the two are joined and the label stock material is further cooled using a second downstream cooling roller. An advantage of the Bayzelon Patents is that the label face stock can be reverse printed on the back side before the label face stock and release paper are laminated, eliminating the need for a subsequent de-lamination and re-lamination of the label face stock from and to the liner downstream in the overall process. Because printing is not done over the adhesive, the Bayzelon Patents eliminate the likelihood of blurred printing on the reverse side of the label face stock. Further, the Bayzelon Patents obviate the need for lengthy equipment to cure the silicone release liner and provide an apparatus that essentially produces a web of labels in multiple label widths married to a release liner in a single pass.
U.S. Pat. No. 7,556,708 (the '708 patent) discloses a method of forming a cut label on a liner by feeding completed label stock material (a label face stock laminated to a release liner) into a station that de-laminates the face stock from the release liner, cuts label material, and then re-laminates the label face stock to the release liner, forming a web of multiple widths of cut labels. The '708 patent process also enables the manufacturing of liner-less labels to be used in liner-less label application equipment by re-laminating the label face stock to a temporary, or carrier, liner that is easily removed by such application equipment. This de-lamination and relamination process is cumbersome, time-consuming and inefficient with respect to the process used to manufacture the present invention. Further the '708 patent does not teach a method enabling reverse printing on the back side of the label face stock.
U.S. Pat. No. 7,815,761 (the '761 patent) teaches a method of creating liner-less labels by using a temporary, or carrier liner, or labels with thin liners. The '761 patent eliminates the de-lamination and re-lamination steps in the label cutting process of the '708 patent by disclosing a cutting method that involves a rotating chilled die cutting head to cut the completed label stock material (face stock laminated to release liner) to provide a matrix around the label shape. The '761 patent process uses a chilled die cutting roller that is chilled to a temperature at or below the glass transition temperature (Tg) of the adhesive (which reduces or eliminates the tackiness of the adhesive) that adheres the label face stock to the liner. The chilled die cutting method cuts through the label face stock easily without slicing through to the liner. The '761 patent also discloses the preferred embodiment of the die cutting of liner-less labels with an exposed adhesive surface by use of the chilled die cutting roller chilled to the Tg of the adhesive. The liner-less labels are laminated to a temporary, or carrier or sacrificial liner so that they can be used in conventional label application equipment. The '761 patent also teaches a method where a carrier or sacrificial liner is used prior to die cutting, a vacuum is used to remove or de-laminate the carrier or sacrificial liner, and then the face stock is laminated to a final liner after die cutting, enabling the use of thinner liners. Temporary, sacrificial or carrier liners may be re-used a limited number of times. After cutting the label shapes in accordance with the '761 patent process, the label is stabilized with respect to the matrix without the use of vacuum. The avoidance of vacuum securement is advantageous with the use of thinner liners which may be more readily deformed than would thicker, heavier release liners. US 2011/0036504 describes an improved cooled die head over that taught in the '761 patent for cutting or perforating label materials.
Like the '708 patent, the '761 patent does not teach a method that enables reverse printing of the label face stock. The present invention is a reverse-printed pressure sensitive label assembly that is manufactured in a way so as to ensure easy short-term removability once a label is applied to the surface of a container for purposes of rework or repositioning. The unique feature of the present invention is that upon short-term removal and repositioning of the label face stock on a container, no ink adheres to the surface of the container as is typical of other prior art labels.